NC remains connected to the power terminal until the pressure builds up. The NC terminal is a great place to connect a 12 volt LED for diagnostics. Connect the 12 volt pilot light from NC to chassis negative.
Then connect a 2nd LED from NO to chassis negative.
Turn key on
First LED glows, YOU HAVE POWER
Pressure builds up
First LED goes out and 2nd LED lights up
THE PRESSURE SWITCH HAS CLICKED ON
Use blinking 12-volt LEDs available on eBay and power consumed by the LEDs is almost immeasurable. I love self diagnostic systems.